Fornia



March 8, 1932. R, H WORRALL 1,843,594

OSCILLATOR CIRCUITS Filed Sept. 6, 1927 III I I I I I I I I iii-ESE i I l I l I mm INVENTOR.

I I fi05e2-Z/. %rra 5;, L Z .461 J By Qymmm W47 AfToRNEy Patented Mar. 8, 1932 UNITED STATES PATENT OFFICE ROBERT E. WORRALL, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGN'OR, BY EESNE ASSIGNMENTS, T FEDERAL TELEGRAPH COMPANY, A CORPORATION OF CALI- FORNIA.

OSCILLATOR CIRCUITS Application filed September 6, 1927. Serial No. 217,815,

My invention relates broadly to high frequency oscillator circuits and more particularly to a circuit arrangement for maintaining constant the frequency of an oscillator.

One of the objects of my invention is to provide a circuit arrangement for an electron I tube oscillator wherein the circuits are arranged for the establishment of high frequency oscillations which may be sustained at a constant frequency.

Another object of my invention is to provide an oscillator circuit wherein variations in plate circuit impedance, grid circuit impedance, filament temperature and plate potential will have a minimum tendency to shift the frequency in the oscillator circuit.

Still another object of my invention is to provide a circuit arrangement for an electron tube oscillator in which body capacity effects are substantially negligible with respect to any tendency to shift the frequency of the oscillator.

Other and further objects of my invention reside in the circuit arrangements for an oscillator, as more fully described in the specification hereinafter following by reference to the accompanying drawings in which:

Figure 1 shows diagrammatically an oscillator circuit arrangement embodying the principles of my invention; Fig. 2 shows a modified arrangement of the oscillator circuit of my invention used in connection with a signal receiving circuit; and Fig. 3 shows a further. modified form of the oscillator circuit of my invention.

Referring to the drawings in detail, the

oscillator circuit arrangement includes variable condenser 1 shunted across the tapped inductance 2 connected in circuit with electron tube 4, with a grid leak and condenser 3 disposed in the grid circuit thereof. The .plate circuit of the oscillator includes the source of potential 10 and a variable by-pass condenser 8. A source of potential 9 is shown for supplying the filament heating current to the filament electrode 4a. Interposed between the source 9 and the filament 4a, I provide two'radio frequency choke coils 5a and 56 which operate to maintain the filament at a high radio frequency potential with respect to the plate or ground terminals. Two fixed condensers 6a and 6b are arranged as shown in Fig. 1 to keep one end of the choke coils 5a and 55 at ground potential by virtue of the ground connection 7 which extends to the mid-point of the condenser circuit, as represented at 11. Thecathode 4a is connected to the tap 12 on the inductance 2 and may be varied to obtain the proper feed-back between the grid and plate circuits for placing the circuit in a condition of oscillation. The condenser 8 serves both as a by-pass condenser and as a means for controlling the strength of oscillations or regeneration. A shield 13 is illustrated entirely enclosing the apparatus and connected to ground through lead 14 and connection 15.

In Fig. 2 I have illustrated the application of the circuit arrangement of my invention to a signal receiving system wherein an emmeter 16 is arranged in the input circuit for indicating that the circuit is oscillating. A blocking condenser'l'? is provided between the tap l2 and the filament circuit 4a to keep the filament direct current from flowing through the plate side of the inductance 2, that is, the portion of the inductance represented at 18, and at thesame time permitting the flow of radio frequency current. A grid bias control is provided by means of the resistance 19 and the variable tap 20, which connects to the grid electrode of the tube through the ground 7 ammeter 16 and the resistance 3. A telephone transformer 21 is arranged in the input circuit for transferring the signaling currents to telephone 22.

In Fig. 3 the inductance 2 is represented as having a portion 18 thereof included in circuit with the filament 4a. A choke coil is represented at the opposite side of the filament circuit. A single condenser 6'0 is shown connected across the filament circuit. The filament temperature is regulated by means of rheostat 24. A condenser 25 is shown connected between the plate electrode and the end of the inductance 2.

With the circuit arrangements of my invention oscillations with a high degree of stability may be sustained over a range from 3,00022,000 kiloeycles. I have successfully circuit. The radio frequency current path in the oscillating circuit is completed through the filament circuit to ground but not through the filament heating system.

I have found that changes in the plate circuit impedance, grid circuit impedance, variations in filament potential and changes in the plate potential cause minimum disturbance with respect to the constancy of the frequency of oscillations when the circuits of the oscillator are arranged according to my invention. Body capacity effects are substantially negligible, for the reason that one side of the variable condensers 1 and 8 are at ground potential and the radio frequency choke coils 5a and 5b isolate the tube filament and maintain it at a high radio fre-v quency potential with respect to ground. At the same time the plate radio frequency circuit operates at low potential as it is grounded in the same manner that one side of the condenser 8 is grounded.

While I have described my invention in certain preferred embodiments, I desire that it be understood that modifications'may be made and that no limitations upon my invention are intended other than are imposed by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is as follows:

1. An oscillator system comprising an electron tube having input and output circuits, a cathode, a cathode circuit, a source of energy for supplying heating current to the cathode circuit, a choke coil disposed in series in each side of said cathode circuit between said source and said cathode, a capacity system connected in shunt between the ends of said choke coils adjacent said source, a connection between said capacity system and a point in said output circuit, and a connection between one side of said cathode and a point in said input circuit for maintaining a high potential on said cathode at the frequency sustained by said circuits.

2. An oscillator comprising an electron tube having grid, filament and plate electrodes, an input circuit including said grid and filament electrodes, an output circuit including said plate and filament electrodes, a filament heating circuit, a source of energy for supplying current to said filament, choke coils connected in said filament heating circuit, each of said choke coils having one terminal thereoiadj'ifent said source, a pair of condensers connected across the ends of said choke coils immediately adjacent said source, and a connection from said output circuit to a. point between said pair of condensers for maintaining a high potential on said filament at a frequency corresponding to the frequen cy sustained by said input and output circuits.

3. An oscillator comprising an electron tube having grid, filament and plate electrodes, an input circuit including said grid and filament electrodes, an output circuit including said plate and filament electrodes, at filament heating circuit, a source of energy for supplying current to said filament, choke coils connected in each side of said filament heating circuit between said source and said filament, each of said choke coils having one terminal thereof adjacent said source, a connection between the end of one of said choke coils at a point adjacent one side of said filament and said input circuit, and a connection between the opposite end of said last mentioned choke coil and the end of the other choke coil remote from said filament with said output circuit for maintaining a high potential on said filament at a frequency corresponding to the frequency sustained by said input and output circuits.

ROBERT H. VVORRALL. 

